KN95 masks offer 95% filtration of airborne particles smaller than 10µm (microns).
With breathing valve - makes breathing OUT easier. Suitable for Plasma Fibroblast treatments. 

*Packaged in lots of 2*
Main characteristics are as follows:
6 ply (not 4) for extra protection
Noxious gas defense
Deodorisation
Filtration bacterium
Filtration of dust particles etc
 
The added breathing valve allows better breathing conditions and one way flow of the breath, out of the mask. Exhaling provides positive pressure to open the valve when, which will expels the exhaled gas effortlessly and without making it hard to breathe. 
 
Different masks have different filtering efficiencies approved by different certifying bodies. Some well known and reputed certifying bodies are BIS (Bureau of India Safety), NIOSH (National institute of occupational safety and health) and GB Standards (Guobiao standards). All these bodies test and certify masks as per different filtering efficiencies such as 80%(FFP1), 95%(N95, KN95) etc.